Disable spell checking

I just came upon this interesting browser by reading a blog [url=http://www.donationcoder.com/forum/index.php?topic=40389.msg377241]article [/url]at donationcoder.com, One of the first things I notice is, that spell checking is active. How can I disable this? All kind of spell checking is mostly distractive for me.

I already tried this, but vivaldi://settings/languages points me just to the settings screen, nothing language specific here. (Latest 1.2.490.39 on OSX).
Going into language settings via right-click in a textbox opens some language dialog, but here I cannot disable spell checking, I can only e.g. remove English then I'm left with an entry "English (United States)".
When I open this language settings dialog again, then again I have 2 entries there English (US) and English (although I removed "English" before), strange…